1. Field
Compositions and methods for hair growth.
2. Background
Androgenic alopecia is the most common form of scalp hair loss in both men and women. It has been estimated that more than 50 percent of men over 50 are affected by the condition and approximately 12 percent of men affected have lost most of their hair by the age of 30. According to the American Academy of Dermatology, by the age of 40, approximately 40 percent of women have begun to experience some hair loss.
Androgenic alopecia is caused by an androgen-dependent process which causes miniaturization of scalp hair follicles. Scalp dihydrotestosterone (DHT), a hair loss promoter formed from testosterone, is believed to be a major initiator of the process. Testosterone is converted into DHT by an enzyne known as 5-alpha reductase (5α-reductase). Men with androgenic alopecia typically exhibit lower levels of total testosterone, higher levels of unbound/free testosterone, and higher levels of total free androgens including DHT. Thus, it is believed that an increase in DHT levels contributes to hair loss.
In women, it has been recognized that when estradiol and progesterone levels are extremely high, such as during pregnancy, an increase in hair growth is experienced. During the postpartum period, however, when estradiol and progesterone levels decrease, hair loss is experienced. Thus, estradiol and progesterone levels are believed to be additional factors which may contribute to hair loss. Estradiol is a steroid derived from cholesterol. Synthesis of estradiol involves a key intermediary androstenedione, a steroid hormone, which is converted to testosterone which in turn undergoes aromatization to estradiol, or, alternatively, androstendione is aromatized to estrone which is converted to estradiol. Progesterone is a naturally occurring steroid hormone belonging to a class of hormones called progestagens and is synthesized from pregnenolone, a derivative of cholesterol.
Thyroid hormone may also play a role in hair loss. In particular, a common complaint of patients suffering from thyroid disease, and in particular hypothyroidism, is hair loss. Hypothyroidism is a disease characterized by insufficient production of thyroid hormone by the thyroid gland. Hormones produced by the thyroid include thyroxine (T4) and triiodothyronine (T3). These hormones regulate the rate of metabolism and affect the growth and rate of function of many other systems in the body. T3, in particular, has been shown in one study to stimulate hair growth in mice with a mutant hairless gene when applied topically. (Safer, Joshua D., Thyroid Hormone and Hair Growth: Clinical and Basic Features; 74th Annual Meeting of the American Thyroid Association, Meet the Professor Workshops, pages 187-193 (Oct. 10, 2002-Oct. 13, 2002)).
Current FDA approved treatments for alopecia condition in males and females include drug based treatments. In particular, FDA approved treatments for males include five percent minoxidil (ROGAINE®) and finasteride (PROPECIA®) administered systemically. For women, topical two percent minoxidil (ROGAINE®) has been approved. Other treatments considered have included herbal extracts.
For the most part, however, the above described treatments, particularly ROGAINE® and PROPECIA®, merely maintain existing hair while having little effect on hair regrowth. In addition, PROPECIA® is not safe for use by women and children and must be prescribed by a physician. Moreover, topical treatments, such as topical applications of minoxidil involve several steps which must be performed in addition to the user's daily hair care regimen twice a day.